From a spotter airplane buzzing off the coast of Baja California, it's hard to miss the dark shape of a giant whale shark moving through the emerald green waters below.

Whale sharks are the world's largest living fish species, growing up to 40 feet (12 meters) long.

They move near the surface, feeding on the plankton and krill that mass in these waters during the winter months.

The Bay of La Paz, though busy with fishing boats and divers, is a safe zone for these rare and threatened animals.

But around the world, shark populations have declined dramatically in recent years, mainly due to overfishing.

Read entire original article at National Geographic News .